Sunday, May 28, 2006

In 2003 Europe was hit by the most extreme heatwave since meteorological measurements began.

Not only where records for max temperature broken but records for highest nighttime temperature, and other aggregate measurements such as the number of consecutive days with very high temperatures. The result of this was over 20 thousand deaths in France and more than 35'000 across Europe.

These temperatures where extreme and prolonged. Although climate change cannot be said to cause any one event there has been serious analysis of the heatwave, an event that can actually be spilt into clusters of occurrences. Analysis of this data shows that overall based on past data, which is actually very good in Europe, the event was several standard deviations away from the norm and is only accurately described as a one in a thousand year or greater event.

The chart above shows the usual average maximum for each day of the month based on previous years, this is shown in black. In red are the actual temperatures in 2003.

The fingerprints of climate change are all over it. This is particularly worrying as, due to the intertia in the climate system, we are currently only experiencing the warming created by GHG emissions of 40-50 years ago; the warming causes the weather patterns that can lead to extreme heatwaves.

According to Stott et. al.

"...with the likelihood of such events projected to increase 100-fold over the next four decades, it is difficult to avoid the conclusion that potentially dangerous anthropogenic interference in the climate system is already underway.Â

"by the end of this century ... 2003 would be classed as an unusually cold summer... "

One US study lead by Dr. Laurence S. Kalkstein is looking at what wouldhappenn if an event with the same degree of abnormality where to occur in the US.This project is currently still in its early stages but one thing is clear, the death toll, without investment inpreparationn, could be similarly large. The first attempt at creating an analogue in the US was done for NYC, and although this gives a slightlyexaggeratedd imaged due to greatervariancee in temperatures inPariss than NYC it still gives a good indication of just how extreme the heatwave was. In the chart above you can see that the highesttemperaturee ever reached in NYC is 106F, if a heatwaveanalogouss to the one that happened in Europe where to affect NYC then 11 days in a row would meet or exceed this record! A new record of around 116F would be set. Also if you look at the night time temperatures you can see that there would be little respite.

The powerpoint presentation and video on which this post is based can be viewed on the Harvard Medical School website.